Waterborne thermoset compositions are curable compositions such as, for example, clear coatings which are frequently applied to substrates by spraying techniques. Some of the common spraying techniques used are, for example, air spray, airless spray, air-assisted airless spray, disc and bell spray, and high volume/low pressure spray. In air spray compressed air is critical to atomize the waterborne thermoset composition and to assist in conveying the droplets to the substrate. In airless, disc, and bell spray techniques the waterborne polymeric composition is atomized by mechanical means and the droplets are suspended in air on formation. Air-assisted airless spray is a hybrid of the two spray methods described above wherein air is used to convey the droplets which are formed mechanically; and high volume/low pressure spray is another commonly recognized variant of air spray.
Waterborne thermoset compositions frequently contain microfoam after they are applied to substrates by various spraying techniques. Microfoam remaining in a dried film formed from the spray-applied aqueous composition may detract from the appearance of the film, particularly from the appearance of a clear, or substantially unpigmented, film, which film may appear to be hazy. In addition the whitish cast which microfoam imparts may be manifested in high whiteness values in colorimetric measurements and in diminished distinctness of image (DOI) values, each with respect to a microfoam-free dried film formed from a composition containing an emulsion-polymerized addition polymer.